Eddy-current electric apparatus



EDDY-CURRENT ELEGIR fC APPARATUS Filed DEC. lO', 1943 39 Z v2:3 z 39 25ifi/25 J P 5 3 I -J /8 Z9 /8/ 7.38V 20 0 g? 778 [25 fa 22 35 352/ 0 3 4]u f gl Z( s J 9] m &'\ x 35 9 5/ f z 7 /3 M 1 49 f /3 6 f I m 7 67 /z 7l3 7;] I 57 Q /l 65 63 T J g 3 V f FIG 5 /s 9 a al /5 I7 /3 ,5 5g 4749 45,7

/z 6R 71%/ M2! 6V 74 3 fl l1 57 Jan. 15,401946:Y 4 Y "i M. WINTHER-EDDYCURRENT ELECTRC APPARATUS Filed Dec, y10, 1943 3 sheets-sheet 2Patented Jan. l5, 1946 Mmm 'r'.mnsnea Waukegan, n1., assignmto Martin P.Winther, Waukegan, Ill., trustee anneau 1o, 1943, sensi No. 513,801

iz clama. (c1. 17a-zw This invention relates to eddy-current electricapparatus, and more speciflcallylto eddy-current couplings, clutches,brakes, dynamometers and the like. 1 Y,

AAmong the several objects of the invention may be noted th'e provisionof an electric eddy-current slip coupling, clutch, brake, dynamometer orthe like having a more constant flux gap over a wide temperature range;the provision of a clutch of the class described having a lowmanufacturing cost because the use of pilot bearings may be avoided inview of said improved vgap condition; the provision of a clutch of theclass described which, by eliminating said pilot bearings, alsoeliminates the usual critical lubricating requirements encounteredtherewith; and the provision of a clutch oi' this class which may bemade with and which retains a vibration tolerance which is less thanthat which could be maintained with said pilot bearings. Other objectswill be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelemental-features of construction, and arrangements of yparts whichwill be exemplified in the structures hereinafter described, and thescope of the application of which will be indicated in the followingclaims.

In the accompanying drawings,- in which are illustrated several ofvarious possible embodiments of th'e invention,

Fig. 1 is a longitudinal section of one form of the invention;

Fig. 2 is a right-end elevation of Fig. 1;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 1:

Fig. 4 is a fragmentary left-end view of Fig. 1;

Fig. 5 is a fragmentary longitudinal section corresponding to the lowerregions of Fig. 1 but showing an alternative form of the invention;

and,

ligJ is a view similar to Fig. 5 and showing anotbsr'slternative form.

Similar reference characters indicate correspending parte throughout theseveral views `of the drawings.

- Thstarmulipolutchandliipeouplingasused air gap, under cold startingconditions, was made as small as possible without actually havingmechanical interference. Becoming warm under operating condition, theouter rotary member, which usually was the eddy-current member, wouldexpand away from the rotating field member or spider, thus considerablyincreasing the air gap. As the torque ratings had to be establishedunder maximum gap conditions, that is, under maximum operatingtemperatures, such ratings were based on the characteristics prevailingwhen the air gap was at a maximum, which, in itself, was satisfactoryenough.

- However, as the coupling cooled to normal room temperature, the airgap would again shrink to the minimum value, and when the coupling wasAagainstarted for a succeeding cycle of operation,

it would, for a time, operate with a small air gap.

Then, if perchance, an operator would fully excite the field under suchconditions of minimum air gap, the eccentric or oil-center forcevgenerated between the magnetic surfaces would be tremendous, even withonly slight variation in the air gap due to misalignment or looseness inthe bear- Off-center pull varies approximately with the inverse squareof the air gap. Thus 1/M-inch air gap will have four times theolf-center pull of a als-inch air gap.

The above made necessary a pilot bearing directly between the drivingand driven members.

One of the remedies was found to be obtained through the use of a copperlining inside of the eddy-current drum of the order of a 11g-inch inthickness. This separated the magnetic members sufliciently to reducethe off-center pull to a value that did not become dangerous to theoperation of the machine when starting. While this was a substantialimprovement, the manufacturing costs of the liner was relatively high.The present invention eliminates both the need for the liner and thepilot bearing and maintains a close air gap when needed, andautomatically prevents formation of too small a gap under startingconditions when not needed, thus minimizing said eccentric loadingcondition.

In order that the objection to a pilot bearing `may be fully understood,it may be explained that the methodof lubricating anti-friction bearingsof this class is by means of grease. It is not very often possible touse oil, unless speciaiprecau- Ations are taken and these precautionsare also costly. Where grease is used, which is by far in most of thecases, centrifugal force will cause the grease to form a circular sheetclinging to the outer surface of the bearing member, which in the caseof a pilot bearing rotates. If the grease content of the bearing isexactly right, the thickness of this layer in the bearing will be suchas to feed a small volume of the grease to 4the bearing constantly. If,however, the grease content is too low, the layer will be so thin thatno grease will enter the bearing. If, on the other hand, the greasecontent is too high, it will form a layer with a considerably smallerinside diameter than the inside diameter of the .ball bearing outerrace. The result is that a copious flow of grease to the bearing isconstantly had with a resultant extreme agitation of the grease withaccompanying generation of heat. This heat soon destroys the grease,volatilizing the lighter ends and before long the bearing is destroyed.Thus it will be seen how critical lubrication of pilot bearings is andhow desirable it is to eliminate it, or take other suitable precautions.

There are other mechanical reasons for avoiding the use of a pilotbearing. For example, the normal tolerances of the eccentricity in suchbearings are not close enough to make the coupling always operatesmoothly. Machines of this type are balanced to a vibration tolerance ofone mil, or .001 inch. The normal eccentric tolerance of a ball bearingis from one and onehalf to three times one mil. Thus a clutch may bebalanced with the bearing running out as low as one mil and be perfectlysmooth until but not after this bearing wears down. Also, a newlyinstalled bearing may run out three mils. Furthermore, if a newly fittedbearing has a run-'out 180 from that of the original bearing, themachine will be very badly out of balance. The difficulty is accentuatedin pilot bearings because these have rotating inner and outer raceswhich must fit tightly in the housing and on the, shaft without physicalplay between the housing and the outer race of the bearing. Thus theeccentricity of the outer race and the inner race are both elements inproducing eccentric rotation of the two members, which would not be acondition met with when using a bearing with a stationary outer race ina stationary housing. In the latter Vcase only the eccentricity of theinner race becomes a factor in the trueness of rotation of the unit.According to the construction herein described only bearings havingstationary outer races are used.

Referring now more particularly to Fig. 1, there is shown at numeral l astationary case made in two cup-shaped halves 3 and 5 which aresubstantially enough identical so that they may be cast from a singlemain pattern. Then, by slight differences in auxiliary loose patternpieces, or in machining as, for example, as the tongue-andgrooved joint1, they may be adapted to one another or other parts. Parts 3 and 5 arethus organized at 1 by means of bolts 9 to form a complete hollow frame.

Each frame member 3 and 5 has similar legs II and also a series ofaxially located ports I3 for air inlet purposes, and a series of radialports I5 for air outlet purposes. Suitable annular screens I1 cover theports I3 and a cylindric screen I9 covers the outlet ports I5. The portsI3 are within annular rings I2 and I4 connected by arms I6. Connected tothe inner rings I4 by means of webs 95 are cylindric bearing sleevesshown at 2I. These carry the outer stationary races 23 of ball bearings25. One set of bearings 25 (the righthand set in Fig. l) support arotary drive shaft 21 and the other set of bearings 25 (lefthand set)support a rotary driven shaft 23.

The shafts 21 and 23 are flanged at their ends as indicated at 3| and 33respectively. The shafts 21 and 29, including the flanges 3i and 33respectively, are preferably made identical. Their end portions arebroken away in Fig, l, but it is to be understood that these areidentical stubs to which the desired driving and driven members arekeyed. The inner races I3 of the bearings 25, as well as otherappurtenances, are held in position by suitable spacing sleeves 20clamped by nuts 22. The identicalness of shafts 21 and 23, along withthe substantial identity between the frame members 3 and l5 is verydesirable from a manufacturing viewpoint.

Suitable inner lubricant-retaining, stationary labyrinths 31 are boltedto the inner ends of the cylinders 2|. These cooperate with rotarylabyrinth members 33 on the rotary shafts respectively. At the outerstub ends 35 suitable oil retainers 39 are used. The labyrinth members31 are held in place by means of studs such as exemplified at numeral4I. The labyrinth members 31 are the ends of spaced cylindric sleevemembers 43 surrounding the cylinders 2l, being spaced' by webs 42 andbolted at the outer ends as indicated at 44. Thus air may flow inbetween rings Il and sleeves 43 on the one hand and the respectivecylinders 2| on the other hand.

On the flange 3| of the driving shaft 21 is bolted a magnetic fieldmember 45 recessed at 41 to provide for an annularly wound field coil 49located between two peripheral rows of tapered, flux concentrating teeth5I. These teeth 5I concentrate the torio flux field generated around theannular coil 49 when the latter is electrically energized. They are alsoextended and tapered endwise to act as air fans. Exciting currentl iscirculated through the coil 43 through suitable slip rings 53 andbrushes 55 (see Figs. l and 2). Wiring between the slip rings and thecoil is not shown, the necessary character of which is obvious.

The armature of the coupling comprises a rotary composite ring indicatedgenerally at numeral 51. This armature is made up in either two or morepieces. depending upon the speed at which it is to .be rotated. Fornominal, or slow speed operation such as 1200 R. P. M., the three pieceform illustrated in Fig. 1 is suitable. In all forms there is used amain cone-shaped supporting member 59 having openings 93, which isbolted to the flange 33 of the driven shaft 28. In the case of the Fig.l, the remainder of the composite ring 51 is made in two identical caststeel halves 6I, welded at the center as exemplined at 63 and elsewhereif necessary, the assembly of the two being welded to the ring 53 as atG5. The reason for having two halves 6I is to meet foundry conditions;otherwise steel castings constituted by rings 6I may be made up in onepiece as indicated at 60 in Fig. 5.

The shapes of the confining rings 6I (Fig. l). and their integralcounter-part 60 (Fig. 5), are of substantial importance to theinventionf They comprise continuous inner rings 81 having smoothcylindric eddy-current surfaces next to the ends of the teeth 5I of thefield member 45. Each ring 61 is initially cast in a continuous form,being connected to its respective outer ring 6I or 60, as the case maybe, by forty-eight (according to the present example) fins 1|approximately one-half inch thick. The fins 1I at their axial ends areextended and tapered as shown at 13 to act as air fans.

After the` eddy-current e been made up by welding parts 59 and 6|(Fig. 1) or parts 59 and 60 (Fig. 5), and has been roughmachined, thespaced inner eddy-current rings 61 are sawed completely through, forexample, at twelve placesin each ring as indicated at 15, the saw beingof approximately 315 inch gauge. Thus each circular eddy-current ringadjacent to the teeth consists of twelve segments 68 indicated in Fig.3. These are supported by the fins 1| and are held in circular positionsby the respective outer solid ring portion 6|.

It will be seen that when the field coil 49 is energized its toric iiuxfield, which is indicated by dotted lines at the bottom of Fig. 1interlinks the field member 45 (including its fluxconcentrating teeth5|), and the members 6| (including the fins 1| and segments 68). Uponrotation of the driving shaft 21, shaft 29 will be driven with some slipby reasonof the magnetic reaction set up due to eddy-current generationprimarily in the segments 68. Most of the eddycurrent generation is inthe segments 68 of the` such generation takes place quite close to thepoint where lines of magnetic flux enter an eddy-current member. Thesegmental rings 61 may therefore be referred to as eddy-current heatingrings.

When the clutch is operated, the segments 68 will become much hotterthan the outer ring portion 6|, because of the temperature drop throughthe fins 1| brought about by air circulation between rings 6| and 61.There may be as much as 100 F. to 125 F. difference in mean temperaturebetween the outer portions 6l and the inner ring segments 68.` However,since the temperature of the outer ring members 6| will determine 'thenormal diameter of the clutch. increase in this diameter is small. Inother words, the spaced segments 68 are more or less held in xed radialpositions by reason of the fact that their supporting fins 1| areanchored on the outside to relatively cool metal in the rings 6|. Statedotherwise, the hottest ring portions of the armature have been bothstructurally isolated and slitted so as to allow peripheral expansion totake place in the slots 15 without commensurate radial expansion. Acontinuous steel ring will increase in diameter approximately rs of 1%for every 150 F. rise in temperature. By cutting up the rings 61 intothe segments 69 by slits 15 any increase in diameter of the inside ofthe segments is only a fraction as much as if the inner eddy-currentsurface were continuous. Thus the flux gap is more nearly constant, atwhatever value is set for it.

- The above remarks all apply to the construction shown in Fig. 5wherein it is to be understood that the rings 61 are also cut up intosegments as above described. The only difference is that the two weldedouter rings 6| of Fig. l are in Fig. 5, cast into (a single outer ring60.

In Fig. 6 is shown a modification of the ininvention for high-speedoperation, say 1300 R.

rings 61 because P. M. or so. In this case, like numerals designate likeparts as in Fig. 1. A rolled or forged steel band ring 11 is shrunk tothe outside of the cast steel rings 6I, and welded thereto as indcatedat 62. It is to be understood that this banded structure can be madealso to apply to the Fig. 5 structure by suitable modification. The bandprovides a structure which will, with drum 51 as a. whole has y moresafety, withstand the added centrifugal forces due to increased speed.

Tapers 13 of the webs 1I act as air'paddles which centrifugally inducea. flow of air through the inlets I3 and to the outlets I5. Some flow ofair is also induced by and between the teeth 5I to flow up around and inbetween the segmental rings 61- and around the cooling webs 1|. Theoutwardly flared shapes of the passages 14 between the rings 6| andblowing action. Thus not only is cooling of ring 61 accomplished, but alarge temperature gradient is maintained-between the outerA continuousrings 6| and the segmental rings 61. n Also, the supporting member 59 ofthe composite armature 51 has the openings 93 therein for accommodatingflow of air. Another feature to be noted in this connection is that thesleeves 43 are spaced from the cylinders 2| and openings are provided atso that air may be drawn in axially between said sleeve 43 and saidcylinders 2| for bearing cooling purposes. Fins 91 on the inside of theinner cone formed by the supporting member 59 of the armature 51 help toinduce a radial flow of air from the center out.

Fig. l shows an auxiliary which .may be used if desired. This is aninduction brake 19 composed of a magnetic ring 8| having inwardlydirected radial teeth 83. An annular coil 65 is carried between the rowsof teeth 63 and when energized sends a torio flux eld through the member8|, including the teeth, and inte-rlinking the outer rin-gs 6I of thedriven rotary member. This induction brake will fit any standard unitand is designed to be used in the kind of service requiring frequentstarting and stopping, but very `little speed reduction for constantoperation.

The brake of course operates to decelerate the output shaft, since it iseffective upon lthe driven drum 51. y

In Fig. 4 is shown an end view of an auxiliary generator unit 81, theinternal operating portions of which are not shown with the exception ofa rotor unit 89 and a stator unit 9|. This item is used in connectionwith associated control apparatus and forms no part of the presentinvention but is shown for completeness of the device as it exists.

It is clear that the principles of the invention may be carried theouter member with teeth 5| extending inward and the armature memberinside with the rings of pads 68 extending outward. In this event thesegmental eddy-current members would be outside of their coolersupporting rings and attached thereto by fins. The same advantages wouldaccrue, namely, that the cool continuous ring would maintain a meanarmature diameter which is more constant than if the eddy-currentsurfaces per se were continuous.

It will also be understood that under the principles of the inventionthe shaft 29 may be the driver and shaft 21 the. driven member, makingthe armature 51 the driver and the field member the driven member. Also,coil 49 may be mounted in member 51, instead of in 49.

In view of the above.it will be seen that the eddy-current armature ofthis machine consists of interrupted rings forming separate segments orpads in which the eddy currents are generated and in which the majorityof Athe heating occurs. The other continuous ring or rings, as the casemay be, provide the entire support for the interrupted rings by means ofconnecting cooling between the inner interrupted fins. The cooling 61Afacilitate centrifugal out by making the field member rings and theouter continuous rings is suiiicient to obtain a substantial workingtemperature difference or gradient between the interrupted eddy-currentrings and the outer supporting rings.

'Ihe fact that the coaxial cylindric extensions 2i reach farther inwardinto the bodies 3 and 5 than outward therefrom provides long steadybearings without occupying much space outside of the device. At the sametime, no pilot bearing is required because of the reduction of oiI-center pull during starting.

It is preferable that the rings 61 forming the segments 68 be of lowcarbon steel because this is best for eddy-current production. Of courseall of the material in the rings B1 and 6| should be magnetic andlikewise the material of the field member 45.

While the slip coupling herein is shown between two rotating members, itmay be between two members one of which is held stationary, as in thecase of an eddy-current dynamometer or a brake and the claims areintended to cover such application of the invention.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. In eddy-current electric apparatus, an inner field-concentratingmember having outwardly directed iiux concentrating teeth, an outerarmature, said member and armature being relatively rotary, meansproviding a iiux iield interlinking the iield member and said armature,the armature comprising an outer continuous ring, at least one innerdiscontinuous ring closely adiacent to the periphery of the field memberand spaced radial cooling and supporting members joining the outercontinuous ring and the inner discontinuous ring, the discontinuous ringcarrying most of the eddy currents and heating while the relatively coolcontinuous ring maintains the discontinuous ring at a substantiallyconstant iiux gap distance with respect to the field-concentratingmember.

2. In eddy-current electric apparatus, an inner rotary ileld member, atleast two peripheral rows of nuit-concentrating teeth thereon, anannular coil in a plane between said rows, a cooperating armature, saidarmature and field member being relatively rotary, the armaturecomprising inner segmental eddy-current rings respectively adjacent tosaid rows of teeth on the field member, a continuous outer supportingring forming part of said armature and supporting said segmental rings,spaced supporting and heat dissipating webs connecting between saidcontinuous supporting ring and the segmental rings, the planes of saidwebs being substantially axial, and the axial sectionbetween the outerand inner armature rings flaring outward from points between the rows ofeld member teeth, said coil generating a toric flux iield interlinkingsaid rows of teeth, said segmental rings, the webs and the outersupporting ring.

3. In eddy-current electric apparatus, an inner rotary field membercomprising an annular coil, outwardly directed radial rows of teeth onopposite sides of said coil, a relatively rotary armature outside ofsaid ileld member and comprising en outer continuous coniining ringmeans oppositev said coil, inner discontinuous eddy-current heatingrings respectively closely adiacent and opposite to said rows of teethon the field member, spaced tins joining said continuous outer ringmeans with the discontinuous inner rings o! the armature, and aperipheral strengthening band around said outer ring means and attachedthereto.

4. In eddy-current field member an annular field coil, radial teeth onthe field member and in the held of said coil, a relatively rotaryarmature and comprising an outer continuous conning ring, an innerdiscontinuous eddy-current heating ring closely sdjacent and opposite tosaid teeth on the eld member and spaced supports joining said continuousouter ring with the discontinuous ring, said continuous outer ring beingjoined to a rotary supporting member located at one axial end of thefield member, separate rotary shafts respectively carrying the iieldmember and the armature, and a frame surrounding said rotary members andseparate bearings independently supporting the shafts in the frame.

5. In eddy-current electric apparatus, an inner rotary field member, anannular field coil, outwardly directed radial rows of teeth in planes onopposite sides of said coil, a relatively rotary armature outside ofsaid eld member and comprising an outer continuous confining ringopposite said coil, inner discontinuous eddy-current heating ringsclosely adjacent and opposite respectively to said rows of teeth on thefield member, and spaced ilns joining said continuous outer ring withthe discontinuous ring, said continuous outer ring being formed in twoparts joined in a median plane, the assembly of said two parts beingjoined to a third supporting member, and an outer band around said outerring.

6. In eddy-current electric apparatus, an inner rotary held member, anannular tleld coil, outwardly directed radial teeth on said coil and inthe eld of said coil, a relatively rotary armature outside of said eldmember and comprising an outer continuous coniining ring, an innerdiscontinuous eddy-current heating ring adiacent and opposite tn saidteeth on the ileld member, spaced webs joining said continuous outerring with the discontinuous ring, and axial extensions from said websadapted to induce a ow of air around the discontinuous inner ring andpast the continuous outer ring.

7. In eddy-current electric apparatus, an inner rotary ileld member, anannular neld coil, outwardly directed radial rows of teeth on oppositesides of said coil and in the field o! said coil, a relatively rotaryarmature outside of said field member and comprising an outer continuousconlining ring opposite said coil, inner discontinuous eddy-currentIheating rings respectively closely adjacent and opposite to said teethon the field member, spaced groups of webs joining said continuous outerring with the discontinuous rings, and opposite axial extensions fromthe respective groups of webs adapted to induce separate flows of airthrough said teeth around the discontinuous inner rings and past thecontinuous outer ring.

8. In an electric clutch, a drive shaft, a driven shaft, a rotary fieldmember on one of the shafts, a rotary armature on the other shaft, ahousing comprising two joined cup-shaped bodies, spaced coaxial inwardextensions forming parts of said bodies and extending farther inwardthan outelectric apparatus, e rotary Y 4 shaft, a rotary field member onone of the shafts,

a rotary armature on the other shaft, a housing comprising twocup-shaped bodies Joined at a median line, spaced coaxial cylindricextensions forming parts of said bodies, flanges on said shafts locatedbetween said coaxial extensions, said rotary members being attached tosaid flanges between said extensions, independent bearing means for saidshafts respectively in said extensions, sleeves spaced from saidextensions and reaching from a region adjacent to the spacing betweensaid extensions to points of attachment with the cup-shaped members,radial openings in said cup-shaped members, axial openings thereincommunicating both outside and inside of said sleeves and adapted todirect air to inside points in the housing, and said sleeves supportinglabyrinth means for retaining lubricant within said bearings.

l0. In eddy-current electric apparatur, an inner rotary field member, anannular field coil, outwardly directed radial teeth on said field memberand in the field of said coil, a relatively rotary armature outside ofsaid fleld member and comprising an outer continuousvconflnlng ring. an

inner discontinuous eddy-current heating ring adjacent and opposite tosaid teeth on the field member, spaced webs joining said continuousouter ring with the discontinuous ring, axial extensions from said websadapted to induce a flow of air around the discontinuous inner ring andpast the continuous outer ring, and axial extensions from said radialteeth cooperating to produce said flow of air.

l1. In eddy-current electric a `ferraille, an eddy-current member, afield .n miser having spaced flux-concentrating means re toward theeddy-current member, said in ibers being relatively rot-aryY meansproviding ay .iiux fiele interlinking said members, said eddy-currentmember comprising a confining ring substantially spaced from the fieldmember, spaced eddy-current segments forming a sectional ring close tothe points of flux concentration from said field member, and spacedsupporting connections between said confining ring and said eddy-currentsegments, whereby the confining ring may be maintained substantiallycooler than the segments and whereby at various higher segmenttemperatures caused by eddy currents therein the flux gap between thesegments and the adjacent flux-concentrating portions of the fieldmember tends to be maintained substantially constant.

12. In eddy-current electric apparatus, a magnetic eddy-current member;a magnetic field member having axial flux-concentrating teeth directedtoward the eddy-current member, said members being relatively rotary, acircular field coil generating a toric flux field interlinking saidmembers and carried by one of them, said eddycurrent member comprising acontinuous magnetic ring portion substantially spaced from the fieldmember, spaced eddy-current magnetic pads forming a sectional ring closeto the points of flux concentration in said field member, and spacedmagnetic supporting connections between said solid ring and saideddy-current pads, said pads, connections and continuous ringaccommodating substantially all of said flux field, circulation of acooling medium being accommodated between the Kpads and the ring tomaintain the ring cooler than the pads, whereby a substantiaily constantflux gap tends to be maintained between the pads and the toothedportions of the field member regardless of temperature variations insaid pads.

MARTIN P. WINTHER.

